Exemplary embodiments of the invention relate to a solid-bowl screw centrifuge.
Solid-bowl screw centrifuges are known in the most diverse embodiments.
For example, German patent document DE 102 03 652 B4 discloses a solid-bowl screw centrifuge with a device for discharging clarified liquid from a drum having a cover with an outlet with which is associated a throttling device, in particular a restrictor plate, the distance of which from the outlet is variable. The outlet furthermore has nozzles for discharge of the clarified liquid which, for saving energy, are correspondingly oriented—especially tangentially—in the circumferential direction.
Nozzles on solid-bowl screw centrifuges and their effect of energy saving in the case of a corresponding orientation at an angle to the drum axis are also known from German patent document DE 39 04 151 A1.
The publication “Patent Abstracts of Japan”, number 11179236 A, in contrast discloses that guide plates can be associated with outlet ports in the drum cover, which are partially closed off in each case by a weir plate forming an overflow weir, which guide plates impart a swirl to the liquid discharging from the drum, wherein the repelling effect that occurs is to be utilized for saving energy. The guide plates are attached on the outer side of the overflow weir, for example on the weir plates. The guide plates are designed as flat plates, for example, which are oriented parallel to the rotational axis of the drum, wherein the plane in which the flat planes lie do not intersect the drum axis and, for example, include an angle of about 45° with the radially extending straight line which extends in each case through the rotational axis of the drum and the respective outlet port.
It is also known—for example from US patent document US 2004/0072668 A1 or PCT International patent document WO 2008/138345 A1—to arrange a housing instead of an overflow weir on the weir plate of the outlet port, wherein the overflow weir or a nozzle is then formed at the outlet port in an inclined side of the housing. These constructions, however, have the disadvantage that co-rotating, relatively complexly formed liquid chambers, which form a part of the rotating system, are formed on the outer side of the drum cover, so that the clarification or separation process continues in the liquid chambers. Undesirable deposits from this separation process can result in the chambers, which involve cleaning problems and out-of-balance problems.
For this reason, German patent documents DE 10 2010 032 503 A1 and DE 10 2010061 563 A1 turn away from the last-described method.
According to German patent document DE 10 2010 032 503 A1, the overflow weir is left directly on the weir plates on the drum cover and the liquid, which has already vacated the rotating system via the overflow weir, is only deflected in the circumferential direction. After discharge from the drum, a clarification effect can no longer occur, the entire discharging liquid jet being deflected through the deflection device in the circumferential direction instead.
According to German patent document DE 10 2010061 563 A1, the weir plate has a material recess forming at least a part of a discharge channel or a complete discharge channel, wherein the discharge channel is designed in such a way that it deflects in a suitable manner flow discharging from the drum.
Consequently, the two embodiments just discussed have proved to be successful. Nevertheless, there is a further demand for optimization, especially with regard to a good energy recovery with simultaneous assurance of a low tendency toward contamination. Exemplary embodiments of the present invention are directed to addressing this problem.
According to exemplary embodiments of the present invention the bottom of the discharge channel is inclined inwardly toward the rotational axis toward the overflow edge relative to the tangential direction by an inclination angle δ at the location of the overflow edge.
A main advantage of this embodiment is again that product deposits cannot easily form, as in the case of the housings in the manner of PCT International patent document WO 2008/138345 A1. Rather, the open design of the discharge channels avoids this disadvantage. In this case, the constructional embodiment is simple and stable. Moreover, the discharging product flow is deflected onto a radial diameter so that a particularly large saving of energy ensues.
Preferably, δ>0° and δ<25°, especially δ≥10° and δ≤20°, apply to the angle δ in this case since a particularly advantageously outflow behavior can be achieved in such a way.